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FRONT END ALIGNMENT
EQUIPMENT REQUIRED
1.
Test Set Models 4EX3A11, 4EX8K12, or 20,000 ohms-per-Volt multimeter with a 1 Volt scale.
2.
A 406-512 MHz signal source.
PRELIMINARY CHECKS AND ADJUSTMENTS
1.
Connect black plug from Test Set to Receiver Centralized Metering Jack J601, and red plug to system board metering jack J905. Set meter sensitivity
switch to the TEST 1 position (or 1-Volt position on 4EX8K12).
2.
For multi-frequency receivers with a frequency spacing up to 0.800 MHz for frequency range of 406-470 MHz, 0.900 MHz for frequency range of 470-494
MHz or 0.750 MHz for frequency range of 494-512 MHz, align the receiver on the channel nearest center frequency.
For multi-frequency receivers with a frequency spacing exceeding the above but no greater than 1.60 MHz for frequency range of 406-470 MHz, 1.80
MHz for frequency range of 470-494 MHz, or 1.50 MHz for frequency range of 494-512 MHz, align the receiver using a center frequency tune-up ICOM.
These limits can be extended to 2.00 MHz, 2.30 MHz and 2.00 MHz respectively, with 3 dB degradation in standard receiver specifications.
3.
With Test Set in Position J, check for regulated +10 Volts. If using multimeter, measure between J905-3 (+) and J905-9 (-).
4.
If using multimeter, connect the negative lead to J601-9 (A-).
5.
Disable Channel Guard.
ALIGNMENT PROCEDURE
METERING POSITION
TEST INTERNAL MULTIMETER TUNING METER
STEP SET METERING -AT J601-9 CONTROL READING PROCEDURE
OSCILLATOR/MULTIPLIER
1. C
(MULT-1)
3
(MULT-1)
Pin 3 C406 Maximum Tune C406 for maximum meter reading.
2. C411, C416,
C306, C307 and
C308
See
Procedure
Preset C411 and C416 to a position similar to C406. Next, preset
C306, C307 and C308 fully counterclockwise. (Minimum capacity.)
3. D
(MULT-2)
4
(MULT-2)
Pin 4 C411, C416,
C406
See
Procedure
Tune C411 and C416 for maximum meter reading. Next, retune
C406, C411 and C416 for maximum meter reading. Then carefully
tune C306 for a change in meter reading (peak or dip).
4. F
(MULT-3)
5
(MULT-3)
Pin 7 C306, C307 &
C308
See
Procedure
Carefully tune C307 and C306 for maximum meter reading. Repeat
the procedure. Next, carefully tune C308 for minimum meter
reading, and retune C306 for maximum meter reading. Do
NOT
readjust C307 and C308.
RF SELECTIVITY
NOTE: IF AMP meter range is 0-700 mVdc with a high impedance DC voltmeter.
5. B 2
(IF AMP)
Pin 1 C301 thru C305,
A303-C2, (and
L2301 if present)
Maximum Apply an on-frequency signal to antenna jack, keeping the signal
below saturation. Then tune C301 through C305 and A303-C2 for
maximum meter reading. In receivers with the UHS preamplifier,
also tune L2301 for maximum meter reading.
6. B 2
(IF AMP)
Pin 1 C301 thru C305,
A303-C2, C306,
C307 and C308
(L2301 if present)
Maximum Apply an on-frequency signal to the antenna jack and slightly tune
C301 through C305, A303-C2, (L2301 if present) for best quieting
sensitivity. C306, C307 and C308 also may be tuned slightly (not to
exceed 1/4 turn).
406-512 MHz MASTR II RECEIVER
Figure 5 - Test Points And Alignment Controls
Figure 6 - Test Setup For 20 Hz Double-Trace Sweep Alignment
LBI-38505 LBI-38505
4